How it works: Linking apps
Link2SD uses a secondary partition on your SD card and uses it as another segment of internal storage.Link2SD moves apk, dalvik-cache (.dex), lib and internal data files into this partition, which the OS mounts on boot, and creates a symbolic link in the original location.
This retains the file structure that the system expects but with the bulk of the data moved to the SD card.

Linking obb and external data folders of apps and games
On devices that have emulated SD card, obb and external data folders are located in the internal storage, not in the external (real) SD card.
Link2SD moves these folders to the 1st or the 2nd partition of your external SD card (depending on your selection) and with the bind option of the mount command remounts the file hierarchy at external SD card while it is still available at the original location.